Higher data speed in cellular phone systems allows offering of new types of services. One of the service types that is expected to have a breakthrough with the launch of GPRS is the Localization Services. These are services providing mobile telephone users with information about where objects or persons are localized. This information may be presented on the user terminal on e.g. a digital map, or simply through statement of position, address or place name.
Further, Location Services may be considered as a network provided enabling technology consisting of standardised service capabilities, which enable the provision of location applications. The main component in LCS is the GMLC (Gateway Mobile Location Centre), to which all location requests are transmitted, providing the requested location from the mobile network. The application(s) may be service provider specific, for example tracking of persons or vehicles. However, the description of the numerous and varied possible location applications that are enabled by this technology are outside the scope of the present document.
As mentioned above, LSC will probably not become common in the GSM environment before the launch of GPRS. However, LSC was specified for GSM already in GSM 03.71, Release 4, but not in originally for GPRS. LSC was introduced in GPRS as late as in the 3GPP TS 23.271 released in 2001.
As a result of this, a large number of GPRS/GSM MSs will support LSC for GSM, but not for GPRS. This applies for MSs that have already been manufactured and for those being manufactured in the near future. Consequently, there will exist a large number of MSs with inconsequent LCS capabilities in many years ahead.
The problem then occurs when an LCS Client (another MS, a service node etc.) wants to track the position of a Mobile Station (MS) via GPRS, i.e. via an SGSN node, and that MS does not support LCS Capability for GPRS.
Due to that LCS for GPRS is standardised in a later release of the standard than LCS for GSM and even later than GPRS itself, it is entirely possible (even likely) to have MSs that support both LCS for GSM and GPRS, but does not support LCS for GPRS.
In this case, if the request for positioning is initially sent to the SGSN node, the positioning may fail in SGSN if the MS does not support LCS for GPRS, whereas if the request had been sent to MSC node (circuit switched GSM), it would have been successful.
The only known solution today is that the SGSN returns an error message, and that the GMLC due to this retransmits the location request towards the MSC.
The problem with the solution as described above is that the fetching of the positioning might be time critical, meaning that the response will be returned to the LCS Client too late if we first have to try against SGSN and then perform a second try against MSC.